This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A375588 #10 Aug 20 2024 09:14:13
%S A375588 1,0,0,6,0,60,720,840,40320,378000,2116800,60207840,598752000,
%T A375588 7792424640,181863601920,2288689603200,45855781171200,
%U A375588 1016682053587200,17113328962329600,422970486434496000,9765438564930048000,213305542403822668800,5916931500898517299200
%N A375588 Expansion of e.g.f. 1 / (1 + x - x * exp(x^2)).
%F A375588 a(n) = n! * Sum_{k=0..floor(n/2)} (n-2*k)! * Stirling2(k,n-2*k)/k!.
%o A375588 (PARI) my(N=30, x='x+O('x^N)); Vec(serlaplace(1/(1+x-x*exp(x^2))))
%o A375588 (PARI) a(n) = n!*sum(k=0, n\2, (n-2*k)!*stirling(k, n-2*k, 2)/k!);
%Y A375588 Cf. A052848, A375589.
%Y A375588 Cf. A357966, A375561.
%K A375588 nonn
%O A375588 0,4
%A A375588 _Seiichi Manyama_, Aug 19 2024